Generally, photolithographic masks are utilized to pattern an energy source such as light as the light passes through the photolithographic mask from one side to another. The patterned light may then be directed towards a photoresist material that has been previously applied to, for example, a semiconductor substrate that is being processed. The patterned light will cause a reaction with photoacid generators located within the photoresist material to form an acid within those areas illuminated by the patterned light. This acid will then react with other components of the photoresist material within the portion illuminated by the energy source to form a chemically distinct polymer. This chemically distinct polymer may then be separated from the unilluminated portion of the photoresist to form either a positive or negative image of the patterned light (depending upon which portion is being removed), in a process known as developing the photoresist. Once the photoresist has been developed, the photoresist may be utilized as a mask during the formation of devices, isolation regions, metallization layers, or other structures on the semiconductor wafer.
The photolithographic masks may themselves be formed utilizing lithographic techniques, whereby a portion of the photolithographic mask is removed to form the desired pattern. This removal process may involve a chemical etchant that reacts with a portion of the photolithographic mask to chemically modify and remove the desired portions of the photolithographic mask.
However, during the patterning of the photolithographic mask, defects can occur that undesirably alter the desired pattern of the photolithographic mask. These defects may occur by blocking too much light, otherwise known as an opaque defect, or by blocking too little light, otherwise known as a clear defect. Unless these defects are fixed, the photolithographic mask will transfer the defective pattern to the semiconductor device, forming defects within the semiconductor device. Such defects may render the semiconductor device inefficient or even unusable.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.